
<?php
class Database {
    private static $instance = null;
    private $conn;

    private function __construct() {
        // Database configuration is loaded from db/config.php
        require_once __DIR__ . '/../db/config.php';

        $host = getenv('DB_HOST') ?: '127.0.0.1';
        $db   = getenv('DB_NAME');
        $user = getenv('DB_USER');
        $pass = getenv('DB_PASS');
        $charset = 'utf8mb4';

        $dsn = "mysql:host=$host;dbname=$db;charset=$charset";
        $options = [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES   => false,
        ];

        try {
            $this->conn = new PDO($dsn, $user, $pass, $options);
        } catch (\PDOException $e) {
            // In a real app, you'd log this error and show a generic message
            throw new \PDOException($e->getMessage(), (int)$e->getCode());
        }
    }

    public static function getInstance() {
        if (self::$instance == null) {
            self::$instance = new Database();
        }

        return self::$instance;
    }

    public function getConnection() {
        return $this->conn;
    }

    // Prevent cloning and unserialization
    private function __clone() { }
    public function __wakeup() { }
}